1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device, which includes a step of forming an anti-reflection coating film for the purpose of increasing fabrication accuracy in the step of photolithography, and a semiconductor device made by this manufacturing method. More specifically, the invention relates to a semiconductor device manufactured by integrating a capacitor and a transistor on a semiconductor substrate, and a manufacturing method of the same.
2. Description of the Prior Art
FIGS. 1 to 3 are sectional views showing a conventional method for manufacturing a semiconductor device having a capacitor and a MOS (Metal Oxide Semiconductor) transistor in the sequence of steps.
First, as shown in FIG. 1A, a field oxide film 62 is formed in a device isolation region of a semiconductor substrate 61 by means of LOCOS (Local Oxidation of Silicon). Also, a gate oxide film 63 is formed on the surface of a transistor forming region of the semiconductor substrate 61 with thermal oxidation.
Subsequently, a polycrystalline silicon film 64 is formed on a surface of the semiconductor substrate 61 so as to serve as a lower electrode of a capacitor (referred to as a capacitor lower electrode, hereinafter) and a gate electrode of a transistor. Then, by introducing high-concentration impurities (dopant) to the polycrystalline silicon film 64, electrical conductivity is provided.
Then, a silicon oxide film 65 is formed as a dielectric film of the capacitor (referred to as a capacitor dielectric film, hereinafter) on the polycrystalline silicon film 64, and a polycrystalline silicon film 66 is formed thereon so as to serve as an upper electrode of the capacitor (referred to as a capacitor upper electrode, hereinafter). Then, by introducing high-concentration impurities to the polycrystalline silicon film 66, electrical conductivity is provided.
Then, as shown in FIG. 1B, a resist pattern 67 is formed on the polycrystalline silicon film 66 so as to plot a shape of the capacitor upper electrode. Then, by using this resist pattern 67 as a mask, etching is performed for the polycrystalline silicon film 66 and the silicon oxide film 65 to form a capacitor dielectric film 65a and a capacitor upper electrode 66a. Subsequently, the resist pattern 67 is removed.
Then, as shown in FIG. 2A, an anti-reflection coating film 68 is formed on a surface of the semiconductor substrate 61. The polycrystalline silicon film 64 and the capacitor upper electrode 66a are covered with the anti-reflection coating film 68. The anti-reflection coating film 68 is then coated with photoresist. After the photoresist is subjected to exposure and development, a resist pattern 69 is formed so as to plot shapes of a capacitor lower electrode and a gate electrode of the MOS transistor.
Then, as shown in FIG. 2B, by using the resist pattern 69 as a mask, etching is performed for the anti-reflection coating film 68 and the polycrystalline silicon film 64 to form a capacitor lower electrode 64a and a gate electrode 64b. Subsequently, the resist pattern 69 is removed. Then, shallow and low-concentration impurities are ion-implanted to both sides of the gate electrode 64b of the semiconductor substrate 61 to form an LDD (Lightly Doped Drain) diffused layer 70 in self-alignment.
Then, a silicon oxide film is formed to be thick on a fill surface above the semiconductor substrate 61, and anisotropic etching is performed for this silicon oxide film. Accordingly, as shown in FIG. 3A, the silicon oxide film is left in the sides of the capacitor lower electrode 64a, the capacitor upper electrode 66a and the gate electrode 64b to form spacers 71. Subsequently, impurities are ion-implanted at relatively high concentration to both sides of the gate electrode 64b of the semiconductor substrate 61 to form impurity diffused regions 72 as a source and a drain of the MOS transistor in self-alignment.
Then, as shown in FIG. 3B, the anti-reflection coating film 68 on the capacitor upper electrode 66a, the capacitor lower electrode 64a and the gate electrode 64b is removed. Subsequently, an interlayer insulating film, a wiring (not shown), and so on, are formed to complete a semiconductor device having the capacitor and the MOS transistor of an LDD structure.
Along with the demand for much higher integration of a semiconductor device in recent years, a gate electrode or the like of a MOS transistor has tended to be shrunk. Thus, a KrF light source or an ArF light source has been used as a light source to be used in a photolithography. Also, for an anti-reflection coating film effective when any one of these light sources is used, a silicon nitride film (SiN) or a silicon oxynitride film (SiON) which is silicon-rich has been used.
It is an object of the present invention to provide a semiconductor device capable of preventing an insulation failure caused by an anti-reflection coating film, and preventing damage to a MOS transistor or a capacitor in etching step during spacer formation by leaving the anti-reflection coating film until spacers are formed. It is another object of the invention to provide a method for manufacturing the above semiconductor device.
In order to achieve the object, as specified in claim 1 and shown in FIG. 7, a semiconductor device of the invention comprises: a capacitor element; and an electrical field effect transistor. In this case, the capacitor includes a capacitor lower electrode (14a) formed on a semiconductor substrate (11) by interpolating an insulating film (12), a capacitor dielectric film (15a) formed on the capacitor lower electrode (14a), a capacitor upper electrode (16a) formed on the capacitor dielectric film (15a) so as to have a shape smaller than that of the same, and an anti-reflection coating film (19) formed on the capacitor dielectric film (15a) exposed to the outside of the upper electrode (16a).
In order to achieve the object, as specified in claim 3 and shown in FIGS. 4 to 7, a manufacturing method of the semiconductor device having the capacitor and the transistor comprises the steps of: forming first insulating films (12 and 13) on a semiconductor substrate (11); forming a first conductive film (14) on the first insulating films (12 and 13); forming a second insulating film (15) on the first conductive film (14); forming a second conductive film (16) on the second insulating film (15); forming an upper electrode (16a) of the capacitor by performing pattering for the second conductive film (16); forming a dielectric film (15a) of the capacitor below the upper electrode (16a) so as to have a shape larger than that of the same by performing patterning for the second insulating film (15); forming an anti-reflection coating film (19) on a full surface above the semiconductor substrate (11); forming a resist pattern (20) by coating the anti-reflection coating film (19) with photoresist and then subjecting the photoresist to exposure and development, the resist pattern being used to plot shapes of a lower electrode of the capacitor and a gate electrode of the transistor; forming a lower electrode (14a) of the capacitor and a gate electrode (14b) of the transistor by using the resist pattern (20) as a mask to perform patterning for the anti-reflection coating film (19) and the first conductive film (14); removing the anti-reflection coating film (19) remaining on the upper electrode (16a) of the capacitor and the gate electrode (14b) of the transistor after the resist pattern (20) is removed; and forming a source and a drain (23) of the transistor by introducing impurities to both sides of the gate electrode (14b) of the semiconductor substrate (11).
In order to achieve the object, as specified in claim 8 and shown in FIGS. 11 to 13, a manufacturing method of the semiconductor device having the capacitor and the transistor comprises the steps of: forming insulating films (42 and 43) on a semiconductor substrate (41); forming a silicon film (44) made of amorphous silicon or polycrystalline silicon on the insulating films (42 and 43); selectively introducing impurities to a dielectric film forming region of the capacitor of the silicon film (44); forming an oxide film (46a) on the impurity introduced portion to be thicker than other portions by performing thermal oxidation for a surface of the silicon film (44); forming a conductive film (47) on a full surface above the semiconductor substrate (41); forming an upper electrode of the capacitor by performing patterning for the conductive film (47); leaving the impurity introduced portion (46a) of the oxide films (46 and 46a) formed with thermal oxidation as a dielectric film of the capacitor while removing the oxide film of the other portion (46); forming an anti-reflection coating film (49) on a full surface above the semiconductor substrate (41); forming a resist pattern (50) by coating the anti-reflection coating film (49) with photoresist and then subjecting the photoresist to exposure and development, the resist pattern being used to plot shapes of a lower electrode of the capacitor and a gate electrode of the transistor; forming a lower electrode (44a) of the capacitor and a gate electrode (44b) of the transistor by using the resist pattern (50) as a mask to perform patterning for the silicon film (44) and the anti-reflection coating film (49); removing the anti-reflection coating film (49) remaining on the upper electrode (47a) and the gate electrode (44b); and forming a source and a drain of the transistor by introducing impurities to both sides of the gate electrode (44b) of the semiconductor substrate (41).
In the manufacturing method of the semiconductor device as specified in claim 3, the second conductive film is formed on the second insulating film as a dielectric film of the capacitor, and the upper electrode of the capacitor is formed by performing patterning for the second conductive film. Then, patterning is performed for the second insulating film to form the dielectric film below the upper electrode to have a shape larger than that of the same. Then, patterning is performed for the conductive film below the dielectric film to form the lower electrode of the capacitor.
Therefore, since the dielectric film is formed to have a shape larger than that of the upper electrode, even if the anti-reflection coating film having low insulation remains above the lower electrode, insulation can be secured between the upper and lower electrodes by the dielectric film.
In the case of a MOS transistor having an LDD structure, insulating spacers are formed in the sides of the gate electrode. In this case, spacers are also formed inevitably in the sides of the upper and lower electrodes of the capacitor. A size of the dielectric film should preferably be decided based on a width of each spacer and alignment accuracy during exposure.
The first conductive film as the gate of the lower electrode of the capacitor and the transistor and the second conductive film as the upper electrode of the capacitor are formed by forming a silicon film made of undoped amorphous silicon or polycrystalline silicon, and then introducing impurities to the silicon film to provide electrical conductivity. Also, the first and second conductive films may be formed by impurity doped silicon by CVD method.
For the second insulating film as the dielectric film of the capacitor, for example, a high dielectric film such as a silicon oxide film, a silicon nitride film, a laminated layer of a silicon oxide film and a silicon nitride film, a tantalum oxide film or the like can be used.
In the case of using a KrF light source or an ArF light source as a light source for exposure of the photoresist, as an anti-reflection coating film, a silicon film, a silicon nitride film which is silicon-rich, a silicon oxynitride film which is silicon-rich or the like can be used. Such a film must have a refractive index of 2.3 or higher in order to function as the anti-reflection coating film. A usual silicon nitride film (good insulating film) has a refractive index of about 2.0 (xc2x10.1). on the other hand, if a silicon nitride film or a silicon oxynitride film having a refractive index of 2.3 or higher is used, the film functions as a satisfactory anti-reflection coating film for the KrF or ArF light source. It is also possible to use a film made of only silicon as an anti-reflection coating film. Such a film made of only silicon has a refractive index of 3.8.
In the case of using a silicon film, a silicon nitride film which is silicon-rich or a silicon oxide and nitride film which is silicon-rich as an anti-reflection coating film, the anti-reflection coating film can be removed by means of wet etching using phosphoric acid or phosphoric acid mixed liquid.
In the manufacturing method of the semiconductor device as specified in claim 8, the silicon film made of amorphous silicon or polycrystalline silicon is formed on the insulating film and, after impurities are selectively introduced to the silicon film, thermal oxidation is performed for the surface of the silicon film. An oxidation rate of the impurity-introduced portion is higher than that of the other portion. As a result, an oxide film is formed on the impurity-introduced portion so as to be thicker than that in the other portion.
Subsequently, the upper electrode of the capacitor is formed on the oxide film formed to be thick, and the oxide film in the portion, to which no impurities have been introduced, is removed. Accordingly, the oxide film remaining below the upper electrode becomes a dielectric film of the capacitor. Then, patterning is performed for the silicon film to form the lower electrode of the capacitor.
Also in this case, since the dielectric film having a shape larger than that of the upper electrode exists below the upper electrode, even if the anti-reflection coating film remains in the side of the upper electrode, insulation can be secured between the upper and lower electrodes.